Any discussion of documents, devices, acts or knowledge in this specification is included to explain the context of the invention. It should not be taken as an admission that any of the material forms a part of the prior art base or the common general knowledge in the relevant art in Australia or elsewhere on or before the priority date of the disclosure herein.
International Patent Application No. PCT/US2000/009080 (WO 2001/017728) by Richard D. Cummins, describes a hand power drill having a drive shaft and a turret that is manually rotatable about an axis set at 45° to the rotational axis of the drive shaft. The turret has two chucks arranged at 90° to one another that are arcuately spaced around the axis of rotation of the turret. A user of the power drill can load each of the chucks with an appropriately-sized drill bit so that each drill bit can be used in turn to conduct a particular operation requiring the use of two bits. To interchange the drill bits the user must hold the pistol-grip of the power drill in one hand and, after disengaging the drill shaft from a first chuck currently at a position of use, manually turn the turret through an angle of 180°. This action brings a second chuck, and corresponding drill bit, to the position of use, wherein the user can then selectively re-engage the drive shaft with this second chuck to facilitate use of that drill bit.
A hand power drill having a similar manually operable multiple chuck change mechanism is described in International Patent Application No. PCT/DK2001/000623 (WO 2002/026453) by Steen Mandsfelt Eriksen. Like the Cummins device, this power drill also has two chucks mounted on a turret that must be manually turned through an angle of 180° in order to interchange the drill bits at the position of use in front of the device.
There are many situations in which a user of a power drill does not have both hands free. If both hands are not free, a user cannot interchange the chucks, and hence the drill bits, without taking a risk of some sort. One such situation occurs when a user is drilling an overhead hole while standing above ground level on a ladder. In order to safely interchange the positions of drill bits when using either one of the power drills described above, a user must descend a ladder to manually turn the turret to bring a new drill bit to the position of use, after which he or she can re-ascend the ladder to continue using the power drill with a new drill bit in place.
In developed counties occupational health and safety (“OH&S”) regulations are continually changing to ensure that peoples lives are not put at risk whilst performing day to day activities at work. In Australia, OH&S regulations stipulate that work with tools on ladders should not necessitate releasing ones grip on the ladder to use a tool. Hence, a single handed automated chuck exchange system for a multiple chuck hand power tool is the only alternative to repeatedly descending and ascending of ladders.
A multiple chuck hand power drill which addresses this very problem, and hence, which includes an automated chuck exchange system and can be operated with a single hand, is described in International Patent Application No. PCT/AU2006/000483 (WO 2006/108220). This application is an earlier application made by the present applicant and its entire disclosure is incorporated herein by this reference. Described in this earlier application is a hand power drill having a plurality of turret mounted chucks which can each be selectively brought to a position of use in front of the tool by way of an automated chuck exchange system. To facilitate the process of automatically switching between chucks at the position of use, the drive shaft of this power drill is reciprocal between first and second axially-spaced locations at which, respectively, the drive shaft is engaged and disengaged from a chuck at the position of use. The positioning of the drive shaft being such that at the second location a drive connection between the drive shaft and the turret is established so that subsequent operation of the drive shaft rotates the turret and interchanges the positions of the chucks at the position of use. The drive shaft being adapted to return to its first location and restore the drive connection with a new chuck at the position of use after the turret has been rotated.
Although the basic principles of the automated chuck exchange system presented in this earlier application remain sound, it has been found that the particular mechanical embodiments that were presented are not ideal from a manufacturing and/or product life stand-point. The preferred embodiments disclosed in this earlier application include gears that are crashed or drawn into mesh with one another only when the drive shaft is moved to its second location. From a manufacturing point of view, this type of gearing arrangement requires precision engineering to ensure that the gears mesh correctly every time the turret is to be rotated. From a product life point of view, crashing and/or constant engaging and re-engaging of gears leads to wear which can result in reduced product life.
It is therefore an object of the present invention to provide a multiple chuck hand tool, preferably a multiple chuck hand power drill, or a multiple chuck tool attachment for a single chuck hand power drill, including an improved automated chuck exchange system.